1. Field of the Invention
The invention relates to a pulse rocket motor with a plurality of solid fuels.
2. Description of the Related Art
A pulse rocket motor has a configuration in which two or more grains are placed in a single pressure vessel so as to be separated from each other by a dividing sheet or wall. This provides the advantage that combustion timing can be differentiated in a solid fuel rocket in which fuel combustion is not easy to stop and restart.
More specifically, a dual pulse rocket motor has been developed, in which a Pulse 1 grain (first grain) is situated in the rear section of a pressure vessel made of a carbon fiber and epoxy resin composition according to the Filament Winding method; a Pulse 2 grain (second grain) in the front section of the pressure vessel; and a barrier insulator (dividing sheet) is disposed between these grains (International Publication No. WO95/30084).
In the dual pulse rocket motor disclosed in International Publication No. WO95/30084, a fore insulator is situated between the pressure vessel and the Pulse 2 grain, and an aft insulator between the pressure vessel and the Pulse 1 grain. The fore, aft and barrier insulators are synthetic rubber made of EPDM (ethylene propylene diene monomer). These insulators are partially overlapped and adhered to each other.
According to the method of producing the dual pulse rocket motor described in International Publication No. WO95/30084, components are placed in order from before backwards. First of all, the fore insulator is placed in the inner surface of the pressure vessel, and the Pulse 2 grain is casted and hardened under vacuum. Secondly, the barrier insulator is attached to the Pulse 2 grain and the fore insulator, and the fore insulator is cut off. The aft insulator is attached to the barrier insulator, and the Pulse 1 grain (first grain) is injected and hardened. The insulators have inner surfaces covered with adhesive liners, which are adhered to their respective grains.
To produce the pressure vessel disclosed in International Publication No. WO95/30084, the carbon fiber and epoxy resin composition is molded directly around the grains according to the Filament Winding method. Pressure vessels thus made from resin have lower rigidity than those made from metal. Furthermore, the production method that molds a pressure vessel directly around grains requires the process of covering the fore, aft and barrier insulators with adhesive liners and thus bonding the insulators to the grains, which complicates the production process.
During the combustion of the Pulse 1 grain, the barrier insulator separating the Pulse 1 grain from the Pulse 2 grain is required to prevent flame from being transferred to the Pulse 2 grain. Due to aging degradation, however, there is the possibility that the barrier insulator and the fore insulator are detached from each other in their adhered region, and thus that the barrier insulator fails to prevent the flame transfer.
During the combustion of the Pulse 2 grain, it is also required that the barrier insulator should be broken at a certain position but never fall in order to prevent the barrier insulator from falling and blocking a nozzle. In this respect, International Publication No. WO95/30084 suggests breaking the barrier insulator in the adhered region between the fore insulator and the barrier insulator. It is not easy, however, to break the barrier insulator with proper timing because the setting of breaking strength by adhesion is difficult. Since the insulators are adhered to the grains, the barrier insulator is constrained from being detached from the grain at the time of the combustion of the Pulse 2 grain, which is a problem from the viewpoint of unfailing working.
The invention has been made to solve the foregoing problem. It is an object of the invention to provide a pulse rocket motor that surely prevents flame from being transferred to a second grain at the time of first pulse and reliably carries out second pulse with a simple configuration.